The electric motor and the generator represented by a motor or an alternator have a single wire of copper, whose electric resistance is low, wound as a wire material around the core of a rotor or a stator, and generates a magnetic field by passing an electric current. The electric current passage of the electric motor and the generator with an outside power-supply unit is often performed with a twisted wire as a lead wire connected to an end of the wire material. Since the twisted wire is composed of a plurality of thin core wires, it has high flexibility and is used generally because it can be wired easily to the power-supply unit or the like.
As a method for connecting the end of this wire material and the twisted wire, there is a method using a caulking terminal. The wire material is connected to one end of the caulking terminal having a caulking part at both ends, and the twisted wire is connected to the other end by caulking. Therefore, there is an advantage that a connection work can be performed easily.
But, the caulking terminal has a disadvantage that the connected portion becomes large because the peripheries of the wire material and the twisted wire are surrounded by the caulking member.
In recent years, a compact and high-power electric motor such as an electric motor for a hybrid car or an electric car is demanded to be made compact including the connected portion of the wire material.
As another connecting method used instead of the caulking terminal, ultrasonic bonding is available. The ultrasonic bonding is a bonding method which uses a device comprising a vibration tool for ultrasonic oscillation and an anvil for fixing a member, holds the member between the vibration tool and the anvil, and applies ultrasonic vibration while pressurizing to cause a diffusion reaction on the interface between two bonding members. Since the ultrasonic bonding does not need to use an additional member such as the caulking terminal, it is effective to make the connected portion compact and to save a space.
A method for ultrasonic bonding of a twisted wire with another member is disclosed in Patent Literature 1. It shows that the twisted wire is previously hardened by ultrasonic bonding, and the hardened twisted wire and another connecting member are additionally bonded by ultrasonic waves. As another bonding member, a connection terminal is disclosed in its embodiments.